Reconfigurable interconnected nodes

ABSTRACT

In the examples provided herein, a system has a plurality of arrayed waveguide gratings (AWG) having a plurality of input ports and a plurality of output ports. A signal within a given wavelength channel transmitted to one of the input ports of a given AWG is routed to one of the output ports of the given AWG based on a signal wavelength. The system also has a plurality of nodes, with each node comprising a set of components for each AWG that the node is coupled to. Each set of components comprises a plurality of optical transmitters, where each optical transmitter is tunable over multiple wavelength channels within a different wavelength band; a band multiplexer to multiplex the multiple wavelength channels within each different wavelength band; and a first output fiber to couple an output of the band multiplexer to one of the input ports of a first AWG.

BACKGROUND

A data center is a facility that stores, manages, and disseminates datausing bandwidth-intensive devices, such as servers, storage devices, andbackup devices. Traffic demands in data centers is ever increasing,leading to upgrading of switches inside the data center to higher speedsto serve the growing demand. However, the bandwidth-intensive devices indata centers are interconnected with optical cables, and physicallychanging the connections between devices can be slow, costly, anderror-prone.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various examples of the principlesdescribed below. The examples and drawings are illustrative rather thanlimiting.

FIG. 1A depicts an example reconfigurable photonic switch.

FIG. 1B depicts example wavelength channels and wavelength bands that atransceiver node may transmit and receive.

FIG. 1C depicts tables showing example wavelength bands that may betransmitted and received by each of the transceiver nodes.

FIG. 1D depicts example components of a transceiver node.

FIGS. 2A-2B show an example two-dimensional configuration ofinterconnected nodes.

FIGS. 2C-2D show different examples of interconnected domains that canbe independently configured.

FIGS. 3A-3B show an example pay-as-you-grow configuration of nodes.

FIG. 4 shows an example three-dimensional configuration ofinterconnected nodes.

FIG. 5 depicts a flow diagram illustrating an example process ofproviding connectivity among nodes.

FIGS. 6A-6B depict a flow diagram illustrating another example processof providing connectivity among nodes.

FIG. 7 depicts a flow diagram illustrating an example process ofreconfiguring interconnectivity of nodes.

DETAILED DESCRIPTION

A system of reconfigurable interconnected nodes includes reconfigurablephotonic switches based upon an arrayed waveguide grating (AWG) thatallow connections between nodes of the system to be reestablisheddynamically without physically changing connections in the system. Theinput ports and output ports of a given AWG are coupled to specifictransceiver nodes. Tunable transmitters are used in the transceivernodes to change the emitted wavelength of a signal, and the connectedAWG automatically routes the signal to a particular output port of theAWG based on the wavelength of the signal. The system of reconfigurableinterconnected nodes can have multiple dimensions, where the number ofdimensions of the system corresponds to the number of different AWGs towhich each node in the system is connected. A controller may be used toconfigure the connections dynamically via software commands sent to thetunable transmitters to change the emitted wavelength.

An AWG may be an M×N port device, where M is the number of input portsand N is the number of output ports. Light at different wavelengthsentering each of the input ports may be demultiplexed into differentoutput ports. When the AWG is operated in the reverse direction, lightentering the output ports may be multiplexed and exit through the inputports.

An AWG operates based upon constructive and destructive interference.Light entering one of the input ports is coupled into a first cavity,and then the light from the first cavity is coupled to one end of anarray of waveguides. The length of each waveguide in the array increasesacross the array, such that the optical path length difference betweenneighboring waveguides introduces wavelength-dependent phase delays. Theother end of the array of waveguides is coupled to a second cavity, andlight from the second cavity is coupled to the output ports of the AWGvia a series of waveguides. Constructive interference occurs when theoptical path length difference of the array of waveguides is equal to aninteger number of wavelengths. As a result, different wavelengths oflight are focused by the AWG into different ones of the output ports.The AWG has a free spectral range (FSR) that characterizes theperiodicity of the demultiplexer. The periodic property arises becauseconstructive interference at the output ports can arise for wavelengthsthat are spaced by a free spectral range.

FIG. 1A depicts an example reconfigurable photonic switch havingmultiple transceiver nodes 121-124 coupled to the input ports 111-114and output ports 115-118 of an AWG 110. In the example of FIG. 1A, theAWG 110 has four input ports 111-114 and four output ports 115-118,however, an AWG in a reconfigurable photonic switch may have any numberof input ports and any number of output ports. For convenience, theinput ports 111-114 of the AWG 110 are labeled A 111, B 112, C 113, andD 114, while the output ports 115-118 are labeled W 115, X 116, Y 117,and Z 118.

Four transceiver nodes 121-124 are shown in the example of FIG. 1A,however, any number of transceiver nodes may be used in thereconfigurable photonic switch. As shown in the inset of FIG. 1A, atransceiver node may include tunable optical transmitters 131-134,receivers 141-144, a band multiplexer 130, and a band demultiplexer 140.While four tunable transmitters 131-134 and four receivers 141-144 areshown in the inset, any number of tunable transmitters and receivers maybe used. An electrical input may enter each transmitter 131-134, theoptical outputs of the transmitters 131-134 may be multiplexed by theband multiplexer 130, and an output waveguide 135, such as an opticalfiber, may exit the band multiplexer 130 carrying the multiplexedsignals. An input waveguide 145, such as an optical fiber, may enter theband demultiplexer 140 carrying multiplexed signals in differentwavelength bands, the demultiplexed wavelength bands may be sent todifferent receivers 141-144, and an electrical output may exit each ofthe receivers 141-144.

The tunable transmitters 131-134 are optical transmitters that emitlight at a central wavelength over a narrow band of wavelengths,referred to as a wavelength channel, and the wavelength of the emittedlight should be tunable over a range of wavelengths across multiplewavelength channels. In some implementations, the tunable transmitter131-134 may be a tunable laser, such as a vertical cavity surfaceemitting laser (VCSEL) or distributed feedback semiconductor laser(DFB), that may be tuned, for example, through the use of a heatingelement. In some implementations, each tunable transmitter 131-134located within a single transceiver node 121-124 may emit light in adifferent wavelength band. In some implementations, each tunabletransmitter 131-134 located within a single transceiver node 121-124 mayemit light in the same wavelength band. In some implementations, sometunable transmitters 131-134 located within a single transceiver node121-124 may emit light in overlapping wavelength bands.

FIG. 1B depicts example wavelength channels and wavelength bands that atransceiver node 121-124 may transmit and receive. Sixteen evenly spacedwavelength channels, labeled 1 through 16 are shown in the graph,however, in some implementations, some wavelength channels may beskipped. In some implementations, the wavelength channels may coincidewith some of the wavelength channels on the wavelength grid specified bythe ITU (International Telecommunication Union), where the wavelengthchannels are spaced by 100 GHz. In FIG. 1B, the first four wavelengthchannels, labeled 1-4, fall within band 1; the second four wavelengthchannels, labeled 5-8, fall within band 2; the third four wavelengthchannels, labeled 9-12, fall within band 3; and the fourth fourwavelength channels, labeled 13-16, fall within band 4. In someimplementations, the wavelength range spanned by one of the bands may bea FSR of the AWG. In some implementations, the wavelength range spannedby one of the bands may include portions of one or multiple FSRs of theAWG.

FIG. 1C depicts tables showing example wavelength bands that may betransmitted and received by each of the transceiver nodes 121-124. Inthe transmitter tables, transmitters are labeled as Txn, where n is thenumber of the transmitter, and following each Txn transmitter label is arow of four possible wavelength channels to which the transmitter may betuned. Each indicated wavelength channel in FIG. 1C is part of anindicator in the format K-MN, where K is the emission wavelength channel(1-16 in this example), M is the input port (A-D in this example) of theAWG to which the transmitter output is coupled, and N is the output port(W-Z in this example) of the AWG to which the transmitter output isrouted.

In some examples, for node 1 121, the emission wavelength of transmitter1 (Tx1) may be tuned to one of the four wavelength channels 1, 2, 3, 4in band 1, and the output of the transmitter may be coupled to port A111 of the AWG 110. If the wavelength is tuned to wavelength channel 1,the light may be routed to output port W 115 of the AWG 110, asindicated by ‘1-AW’; if the wavelength is tuned to wavelength channel 2,the light may be routed to output port X 116 of the AWG 110, asindicated by ‘2-AX’; if the wavelength is tuned to wavelength channel 3,the light may be routed to output port Y 117 of the AWG 110, asindicated by ‘3-AY’; and if the wavelength is tuned to wavelengthchannel 4, the light may be routed to output port A 118 of the AWG 110,as indicated by ‘4-AZ’. Similarly, in some examples, transmitter 2 (Tx2)may be tuned to one of four wavelength channels 5, 6, 7, 8 in band 2;transmitter 3 (Tx3) may be tuned to one of four wavelength channels 9,10, 11, 12 in band 3; and transmitter 4 (Tx4) may be tuned to one offour wavelength channels 13, 14, 15, 16 in band 4. The outputs of thefour transmitters may be multiplexed by multiplexer (mux) 130 and sentto input port A 111 of the AWG 110.

The transmitters in the other nodes, node 2 122, node 3 123, and node 4124, may operate similarly, where each of the transmitters may be tunedto one of four wavelength channels. The light emitted by the fourtransmitters in each node may be multiplexed together using a bandmultiplexer 130 and sent to a different input node of the AWG. The bandmultiplexer 130 may multiplex or couple each of the optical outputs fromthe tunable transmitters 131-134 onto a single output fiber 135. Theband multiplexer 130 may be implemented with different technologies,such as thin film filters, fused fibers, and microring resonators. Themultiplexed output from node 2 122 may be coupled to input node B 112 ofthe AWG; the multiplexed output from node 3 123 may be coupled to inputnode C 113 of the AWG; and the multiplexed output from node 4 124 may becoupled to input node D 114 of the AWG.

If the wavelength range spanned by each of the bands 1, 2, 3, 4coincides with the FSR of the AWG, wavelength channels 1, 5, 9, 13 areeach separated by a FSR, and thus, are routed to the same output port ofthe AWG when entering the AWG at the same input port. Similarly, ifwavelength channels 2, 6, 10, 14 are each separated by a FSR, they arerouted to the same output port of the AWG when entering the AWG at thesame input port; if wavelength channels 3, 7, 11, 15 are each separatedby a FSR, they are routed to the same output port of the AWG whenentering the AWG at the same input port; and if wavelength channels 4,8, 12, 16 are each separated by a FSR, they are routed to the sameoutput port of the AWG when entering the AWG at the same input port.

Returning to node 1 121, a waveguide, such as an optical fiber, couplesthe output port W 115 of the AWG 110 to a demultiplexer 140 via opticalwaveguide 145. Demultiplexer 140 separates the light exiting output nodeW 115 into four bands: light from band 1 may be directed to receiverRx1, light from band 2 may be directed to receiver Rx2, light from band3 may be directed to receiver Rx3, and light from band 4 may be directedto receiver Rx4. Similar to multiplexer 130, the demultiplexer 140 maybe implemented with different technologies, such as thin film filters,fused fibers, and microring resonators.

FIG. 1C also depicts example receiver tables for each of the transceivernodes 121-124 in a similar format as for the transmitter tables. In thereceiver tables, receivers are labeled as Rxn, where n is the number ofthe receiver, and following each Rxn receiver label is a row of fourpossible wavelength channels that the receiver may receive from thedemultiplexer. Each wavelength is part of an indicator in the formatK-MN, where K is the received wavelength channel (1-16 in this example),M is the input port (A-D in this example) of the AWG from which thelight was routed, and N is the output port (W-Z in this example) of theAWG to which the receiver's demultiplexer is coupled.

As indicated in the example receiver table for node 1 121 in FIG. 1C,receiver Rx1 may receive wavelengths in band 1: wavelength channel 1from input node A 111 of the AWG; wavelength channel 2 from input node D114 of the AWG; wavelength channel 3 from input node C 113 of the AWG;and wavelength channel 4 from input node B 112 of the AWG. Receiver Rx2may receive wavelengths in band 2: wavelength channel 5 from input nodeA 111 of the AWG; wavelength channel 6 from input node D 114 of the AWG;wavelength channel 7 from input node C 113 of the AWG; and wavelengthchannel 8 from input node B 112 of the AWG. Receiver Rx3 may receivewavelengths in band 3: wavelength channel 9 from input node A 111 of theAWG; wavelength channel 10 from input node D 114 of the AWG; wavelengthchannel 11 from input node C 113 of the AWG; and wavelength channel 12from input node B 112 of the AWG. Receiver Rx4 may receive wavelengthsin band 4: wavelength channel 13 from input node A 111 of the AWG;wavelength channel 14 from input node D 114 of the AWG; wavelengthchannel 15 from input node C 113 of the AWG; and wavelength channel 16from input node B 112 of the AWG.

Similarly, in node 2 122, receivers Rx5, Rx6, Rx7, Rx8 may be coupledvia a demultiplexer to output port X 116 of the AWG 110; in node 3 123,receivers Rx9, Rx10, Rx11, Rx12 may be coupled via a demultiplexer tooutput port Y 117 of the AWG 110; and in node 4 124, receivers Rx13,Rx14, Rx15, Rx16 may be coupled via a demultiplexer to output port Z 118of the AWG 110. Also, receivers Rx5 in node 2 122, Rx9 in node 3 123,and Rx13 in node 4 124 may receive wavelengths in band 1; receivers Rx6in node 2 122, Rx10 in node 3 123, and Rx14 in node 4 124 may receivewavelengths in band 2; receivers Rx7 in node 2 122, Rx11 in node 3 123,and Rx15 in node 4 124 may receive wavelengths in band 3; and receiversRx8 in node 2 122, Rx12 in node 3 123, and Rx16 in node 4 124 mayreceive wavelengths in band 4.

In some implementations, each of receivers Rx1, Rx2, Rx3, Rx4 may beidentical and capable of detecting light in any of the wavelength bands1, 2, 3, 4, for example, a photodetector or a charge-coupled device(CCD).

In some implementations, to reduce the costs of the reconfigurablephotonic switch, each transceiver node may include an integratedtransceiver, such that the plurality of optical transmitters, theplurality of receivers, the band multiplexer, and the band demultiplexerare integrated on a single die or chip. Examples of suitable diematerials include silicon and indium phosphide.

FIG. 1D depicts example components of a transceiver node. In addition tothe tunable transmitters 131-134, receivers 141-144, band multiplexer130, and band demultiplexer 140 described above, a transceiver node mayalso include modulators 151-154, one modulator for each tunabletransmitter. The modulators 151-154 may modulate the emitted light ofeach of the tunable transmitters 131-134, where the modulation of theoutput of the transmitters is the data to be transmitted from thetransceiver node to a different transceiver node. Examples of modulators151-154 may include a direct modulator that modulates the currentdriving the tunable transmitter 131-134 or an external opticalmodulator, such as a Mach-Zehnder modulator, an electro-absorptionmodulator that modifies the absorption of a semiconductor material whenan external electric field is applied, or an electro-optic modulatorthat modifies the refractive index of a material under the applicationof an external electric field and is used in conjunction with aninterferometric structure.

FIGS. 2A-2B show an example two-dimensional 5×5 configuration ofinterconnected nodes reconfigurable via wavelength switching, where eachnode is connected to two AWGs. In the example of FIG. 2A, there are 25nodes, N11-N55, shown in a five-by-five array. Note that the number ofnodes in each dimension may be greater than or less than five. Each nodeN11-N55 may be a transceiver node, similar to the transceiver node shownin the example of FIG. 1D, except with five transmitters, modulators,and receivers, rather than four, to allow communication with five nodesvia a routing AWG, and the transmitters are each tunable over fivewavelength channels.

Each row of five nodes is connected via two optical fibers, an inputoptical fiber and an output optical fiber, to a different AWG 301-305.For clarity, each line connecting a node to an AWG represents these twofibers. Nodes N11-N15 are connected to AWG 301; nodes N21-N25 areconnected to AWG 302; nodes N31-N35 are connected to AWG 303; nodesN41-N45 are connected to AWG 304; and nodes N51-N55 are connected to AWG305. Each node may communicate to a connected AWG using one of fivedifferent wavelength channels. Each AWG 301-305 has five input ports andfive output ports. Thus, the nodes in the horizontal dimension areoptically interconnected in a mesh.

Additionally, each column of five nodes are also connected via twoadditional optical fibers, an input optical fiber and an output opticalfiber, to a different AWG 311-315, as shown in FIG. 2B. Again, forclarity, each line in FIG. 2B connecting a node to an AWG representsthese two fibers. Nodes N11-N51 are connected to AWG 311; nodes N12-N52are connected to AWG 312; nodes N13-N53 are connected to AWG 313; nodesN14-N54 are connected to AWG 314; and nodes N15-N55 are connected to AWG315. Each node may communicate to a connected AWG using one of fivedifferent wavelength channels. Each AWG 311-315 has five input ports andfive output ports. As a result, the nodes in the vertical dimension arealso optically interconnected in a mesh.

FIGS. 2A and 2B together show all the AWGs in the system and theirconnections to the same 25 nodes N11-N55. For clarity, AWGs 301-305 areshown in FIG. 2A, while AWGs 311-315 are shown separately in FIG. 2B.However, nodes N11-N55 are simultaneously connected to AWGs 301-305 andAWGs 311-315. While nodes N11-N55 are shown in a five-by-five array, thenodes may be in different physical locations. For example, the nodes maybe scattered around a data center, and the AWGs may be located in acentral location in the data center. In this case, the fibers from thenodes connect to the AWGs at the central location, similar to astar-type network.

A first node, for example N11, may communicate via a second node, forexample N51, with a third node, for example, N55. Thus, N11 transmits asignal at an appropriate wavelength channel for the AWG 311 to route thesignal to N51. Then N51 transmits the signal at an appropriatewavelength channel for AWG 305 to route the signal to N55. Tocommunicate from a node in a first dimension to a node in a seconddimension, one electrical conversion of the signal occurs at theintermediate second node.

A system of nodes that has tunable wavelength transmitters and areinterconnected via AWGs may be able to provide multiple paths betweennodes. For example, as discussed above, node N11 may communicate withnode N55 via node N51. However, if N51 were to fail, the system isresilient. Node N11 may still communicate with node N55 via node N15 bychanging the transmission wavelength channel of the signal emitted fromnode N11 such that the signal is re-routed by AWG 301 to node N15. Inthis case, there is still a single electrical conversion of the signalat the intermediate node N15.

FIGS. 2C-2D show different examples of interconnected domains in atwo-dimensional (5×5) configuration of interconnected nodes, where eachdomain can be independently configured using wavelength switching. Adomain may be a group of nodes reserved for communications for a singleentity, such as a customer, enterprise, or business. With the wavelengthswitching techniques described above, it may be possible to physicallyshare a data center, for example, one that supports cloud applicationsfor different entities, while maintaining security of the data withinthe domain of each entity sharing the data center. With other types ofshared data centers, two or more entities may share a node within a datacenter, and privacy of the data is based upon data encryption. In thisscenario, if an entity receives a packet with the wrong encryption, theentity discards the packet. However, receiving the wrong encrypted datapacket provides an opportunity for hackers to access the data. Incontrast, with nodes and domains in a data center dedicated to anentity, as described in this disclosure, specific wavelength channelsare used to communicate among the nodes within a domain, and datapackets are no longer permitted to be routed to a node associated withthe wrong entity. This adds a layer of protection beyond just encryptingthe data, which can result in data packets that are misrouted to anunintended recipient.

Additionally, different domains may be useful for different softwareapplication problems or work flows. For example, some problems may makeuse of a large bandwidth between a small number of nodes, while otherproblems may use a large number of nodes with a smaller bandwidthbetween nodes. Bandwidth may be flexibly assigned to different nodes anddifferent numbers of nodes using wavelength switching and AWGs.

In the example of FIG. 2C, four domains are shown. A first domain hasnodes N11, N12, N21, and N22; a second domain has nodes N13, N14, N15,N23, N24, and N25; a third domain has nodes N31, N32, N41, N42, N51, andN52; and a fourth domain has nodes N33, N34, N35, N43, N44, N45, N53,N54, and N55. Each domain has multiple paths between any two nodes inthe domain in a different dimension, thus providing resilience for thenetwork. For example, for the second domain, node N13 may communicatewith node N24 via either node N14 or node N23.

In the example of FIG. 2D, a different set of four domains is shown. Afirst domain has nodes N11, N15, N51, and N55; a second domain has nodesN12, N13, N14, N22, N23, N24, N32, N33, and N34; a third domain hasnodes N21, N25, N31, N35, N41, and N45; and a fourth domain has nodesN42, N43, N44, N52, N53, and N54. Again, each domain has multiple pathsbetween any two nodes in the domain in a different dimension. Note thatbecause the nodes may be physically located anywhere in a data center,the nodes within a domain do not need to be adjacent. For example, forthe first domain, node N11 may communicate with node N55 via either nodeN15 or node N51.

FIGS. 3A-3B show an example pay-as-you-grow configuration ofinterconnected nodes. In a data center, passive network components, suchas the optical fibers and the AWGs, are less expensive components, whilethe hardware at a node, such as transmitters, receivers, and modulators,are more expensive components. In some implementations, an entity maynot want to pay for the hardware at more nodes than are currently neededor expected to be needed in the near future. A system of reconfigurableinterconnected nodes via wavelength switching is suited to support apay-as-you-grow network. For example, in a two-dimensional 4×4configuration of nodes connected using wavelength switching, the passivenetwork elements that are less expensive may be initially installed, aswell as the hardware for four of the nodes, N11, N12, N21, N22, asindicated in FIG. 3A. The hardware in the remaining nodes of the networkmay not be installed to save expenses.

In a first dimension (rows of the 4×4 configuration), nodes N11 and N12are connected to AWG1, and nodes N21 and N22 are connected to AWG2. In asecond dimension (columns of the 4×4 configuration), nodes N11 and N21are connected to AWG3, and nodes N12 and N22 are connected to AWG4. Thetransmitters at the nodes are tunable over four wavelength channels (tosupport the 4×4 configuration), and the node has a set of fourtransmitters, four modulators, four receivers, a band multiplexer, and aband demultiplexer, as shown in FIG. 1D, for each dimension of thenetwork. In this case, the network has a dimension of two, with eachnode being connected to two AWGs, so each node has two sets of thehardware. Each node may be operated at full bandwidth capacity, forexample, if the hardware can modulate a signal up to 25 GHz, then 25 GHzsignals at each of the four wavelength channels provides a total of 100GHz bandwidth transmission capacity at each node to communicate with theother node connected to the same AWG. Thus, for example, node N11 maycommunicate at 100 GHz bandwidth to node N12, and N11 may alsocommunicate at 100 GHz bandwidth to node N21.

In the example of FIG. 3B, the hardware for two additional nodes N13,N23 have been added. Each of these nodes also has two sets of hardware,four transmitters, four modulators, four receivers, a band multiplexer,and a band demultiplexer. Node N13 is connected to nodes N11 and N12 viaAWG1; node N23 is connected to nodes N21 and N22 via AWG2; and nodes N13and N23 are connected via AWG5. In this 2×3 configuration, the fourwavelength channels at which each node communicates may be provisionedin any manner between nodes. For example, the four wavelength channelsproviding 100 GHz bandwidth from node N11 may be split so that twowavelength channels at 25 GHz each may be routed by AWG1 to node N12,and the remaining two wavelength channels at 25 GHz each may be routedby AWG1 to node N13. In another example, three wavelength channels at 25GHz may be routed by AWG1 to node N12, and the remaining wavelengthchannel at 25 GHz may be routed by the AWG1 to node N13. Thedistribution of bandwidth by the other AWGs may also be provisioned in asimilar manner, as desired.

The remaining nodes in the 4×4 configuration may be added as the entitygrows. Alternatively or additionally, some of the other nodes may beused by another entity in a separate domain.

The above examples show a two-dimensional configuration where each nodeis coupled to two AWGs, one in each dimension. The number of dimensionsis not limited to two; any number of dimensions may be implemented. Inthe example of FIG. 4, a three-dimensional configuration of nodesinterconnected using wavelength switching is depicted. In athree-dimensional configuration, each node is connected to threedifferent AWGs, one in each dimension. The number of nodes in eachdimension determines the number of wavelength channels each tunabletransmitter should be able to emit. Further, each node should have a setof hardware for each dimension. Specifically, the hardware shouldinclude: a plurality of optical transmitters, where each opticaltransmitter is tunable over multiple wavelength channels within adifferent wavelength band; a band multiplexer to multiplex the multiplewavelength channels within each different wavelength band; a banddemultiplexer to demultiplex the multiple wavelength channels withineach different wavelength band; a plurality of receivers to receivewavelengths of light within the different wavelength bands from the banddemultiplexer. For each node, there is an output fiber coupled to anoutput of each band multiplexer and coupled to one of the input ports ofan AWG in each dimension, and there is an input fiber coupled to aninput to the band demultiplexer and coupled to one of the output portsof an AWG in each dimension.

With a 4×4×4 configuration of nodes, a total of 64 nodes may beinterconnected using only four wavelength channels being emitted fromeach node and three connections from each node, one connection to an AWGin each dimension. As an example, for a 4×4×4 system, node N111 maycommunicate with node N444 via nodes N141 and N441. In this case, withthree dimensions, two electrical conversions are used in thecommunications between nodes N111 and N444. The system also providesmultiple paths between nodes for resilience. For example, N11 maycommunicate with node N444 via nodes N141 and N144.

In some implementations, two or more parallel systems of the 4×4×4system shown in FIG. 4 may be used to increase the bandwidth capacity toand from each node. For example, node N111 may communicate with nodeN141 using a single wavelength channel at 25 GHz bandwidth in a first4×4×4 system, and node N111 may communicate with node 141 using a singlewavelength channel at 25 GHz in a second 4×4×4 system, thus providing atotal of 50 GHz bandwidth between nodes N111 and N141. While the exampleof parallel systems of 4×4×4 interconnected nodes is described, two ormore parallel systems may be used for any size system of interconnectednodes to provide additional bandwidth between nodes. With parallelsystems, each node may be coupled to a different AWG in a givendimension for each parallel system. For example, with three parallel4×4×4 systems, a node may be coupled to three different AWGs in a firstdimension, three different AWGs in a second dimension, and threedifferent AWGs in a third dimension, for a total of nine connections toAWGs for each node.

A controller 410 may be used to tune the emission wavelength channel ofthe tunable transmitters in the nodes N111-N444. The controller 410 maybe a single controller or a distributed controller. The tunabletransmitters may be tuned by the controller to the particular emissionwavelength channel that will cause the corresponding AWG to which a nodeis connected to route the signal to the appropriate output port to beaddressed. In some implementations, the controller 410 may use a look-uptable that provides a corresponding output port for each emissionwavelength channel, and each transmitter has its own look-up table.Further, by controlling the emission wavelength channel of each of theoptical transmitters in the transceiver nodes, the controller 410 mayprevent collisions from occurring within the system of nodes by ensuringthat emission wavelength channels of two different optical transmittersare not transmitted simultaneously to a same receiver via the AWGs. Acontroller may be used for any size reconfigurable system ofinterconnected nodes to control the wavelength channels transmitted bythe nodes.

In some implementations, system of interconnected nodes reconfigurablevia wavelength switching includes a plurality of arrayed waveguidegratings (AWG) having a plurality of input ports and a plurality ofoutput ports, wherein a signal within a given wavelength channeltransmitted to one of the input ports of a given AWG is routed to one ofthe output ports of the given AWG based on a signal wavelength. Thesystem also includes a plurality of nodes, each node including a set ofcomponents for each AWG that the node is coupled to. Each set ofcomponents includes a plurality of optical transmitters, where eachoptical transmitter is tunable over multiple wavelength channels withina different wavelength band; a band multiplexer to multiplex themultiple wavelength channels within each different wavelength band; anda first output fiber to couple an output of the band multiplexer to oneof the input ports of a first AWG. Each set of components can alsoinclude a plurality of receivers to receive wavelengths of light withinthe different wavelength bands; a band demultiplexer to demultiplex themultiple wavelength channels within each different wavelength band; anda first input fiber to couple one of the output ports of the first AWGto an input of the band demultiplexer.

In some implementations, each set of components of each node includes anintegrated transceiver, such that the plurality of optical transmitters,the plurality of receivers, the band multiplexer, and the banddemultiplexer are integrated on a single die. In some implementations,each set of components of each node may include a plurality ofmodulators, one modulator for each of the plurality of opticaltransmitters to modulate light emitted by the optical transmitters. Insome examples, each of the optical transmitters of the plurality ofnodes is further tunable over the different wavelength bands, and theband multiplexer and band demultiplexer are tunable.

In some implementations, the system of interconnected nodes may alsoinclude a controller to control an emission wavelength channel of eachof the optical transmitters in the plurality of nodes such that emissionwavelength channels of two different optical transmitters are nottransmitted simultaneously to a same receiver via the plurality of AWGs.

FIG. 5 depicts a flow diagram illustrating an example process 500 ofproviding connectivity between nodes. At block 505, a tunable wavelengthoptical transmitter at a first node may be caused to transmit over afirst fiber an optical signal at a first wavelength channel. The firstfiber is coupled to an input port of a plurality of input ports of afirst arrayed waveguide grating (AWG), and the signal is routed to afirst output port of a plurality of output ports of the first AWG basedon the first wavelength channel and is transmitted over a second fiberto a second node.

At block 510, a tunable wavelength optical transmitter at the secondnode may be caused to transmit over a third fiber the optical signal ata second wavelength channel. The third fiber is coupled an input port ofa plurality of input ports of a second AWG, and the signal is routed toa first output port of a plurality of output ports of the second AWGbased on the second wavelength channel and is transmitted over a fourthfiber to a third node.

FIGS. 6A-6B depict a flow diagram illustrating another example processof providing connectivity between nodes.

In some implementations, a first node and a second node may be part of afirst set of nodes, and a second node and a third node may be part of asecond set of nodes. Each node of the first set of nodes includes aplurality of optical transmitters, wherein each optical transmitter istunable over multiple wavelength channels within a different wavelengthband; a band multiplexer to multiplex the multiple wavelength channelswithin each different wavelength band; a band demultiplexer todemultiplex the multiple wavelength channels within each differentwavelength band; a plurality of receivers to receive wavelengths oflight within the different wavelength bands from the band demultiplexer;an output fiber coupled to an output of the band multiplexer and coupledto one of the input ports of the first AWG; and an input fiber coupledto an input to the band demultiplexer and coupled to one of the outputports of the first AWG.

Each node of the second set of nodes includes a plurality of opticaltransmitters, wherein each optical transmitter is tunable over multiplewavelength channels within a different wavelength band; a bandmultiplexer to multiplex the multiple wavelength channels within eachdifferent wavelength band; a band demultiplexer to demultiplex themultiple wavelength channels within each different wavelength band; aplurality of receivers to receive wavelengths of light within thedifferent wavelength bands from the band demultiplexer; an output fibercoupled to an output of the band multiplexer and coupled to one of theinput ports of the second AWG; and an input fiber coupled to an input tothe band demultiplexer and coupled to one of the output ports of thesecond AWG.

At block 605, an entity associated with the first, second, and thirdnode may be determined. For example, it may be determined that thefirst, second, and third nodes serve the communication needs of a singleentity or customer.

At block 610, the signal at the first wavelength channel may bepermitted to be transmitted from the first node to be routed to thesecond node by the first AWG if the entity associated with the firstnode and the entity associated with second node is the same. That is, ifthe entity or customer served by the first node and the second node aredifferent, then communication from the first node to the second node isnot permitted.

At block 615, the signal at the second wavelength channel may bepermitted to be transmitted from the second node to be routed to thethird node by the second AWG only if the entity associated with thesecond node and the entity associated with the third node is the same.That is, if the entity or customer served by the second node and thethird node are different, then communication from the second node to thethird node is not permitted. Blocks 610 and 615 are a security measureto prevent information from being sent to the wrong destination andpotentially intercepted by an unintended recipient.

Assuming that the first node and the second node are associated with thesame entity, at block 620, a tunable wavelength optical transmitter atthe first node may be caused to transmit over a first fiber an opticalsignal at a first wavelength channel. The first fiber is coupled to aninput port of a plurality of input ports of a first arrayed waveguidegrating (AWG), and the signal is routed to a first output port of aplurality of output ports of the first AWG based on the first wavelengthchannel and is transmitted over a second fiber to a second node.

Assuming that the second node and the third node are associated with thesame entity, at block 625, a tunable wavelength optical transmitter atthe second node may be caused to transmit over a third fiber the opticalsignal at a second wavelength channel. The third fiber is coupled aninput port of a plurality of input ports of a second AWG, and the signalis routed to a first output port of a plurality of output ports of thesecond AWG based on the second wavelength channel and is transmittedover a fourth fiber to a third node.

In one example, the signal may be rerouted from the first node via afourth node to the third node and bypass the second node. For example,the second node may have developed a failure, or the second node may beshut down to save power. In this case, at block 630, the tunablewavelength optical transmitter at the first node may be caused totransmit the signal at a third wavelength channel over the first fiberto the input port of the first AWG. The signal is routed to a secondoutput port of the first AWG based on the third wavelength channel, andis transmitted over a fifth fiber to the fourth node.

At block 635, a tunable wavelength optical transmitter at the fourthnode may be caused to transmit the signal at a fourth wavelength channelover a sixth fiber to a second input port of the second AWG. The signalis routed to a second output port of the second AWG based on the fourthwavelength channel, and is transmitted over a sixth fiber to the thirdnode. In some implementations, the multiple wavelength channelscomprises a first set of wavelength channels and a second set ofwavelength channels, wherein the first set of wavelength channels andthe second set of wavelength channels are distinct, and further whereinthe first set of wavelength channels received by the first AWG from thefirst node is directed to the second node, and the second set ofwavelength channels received by the first AWG from the first node isdirected to the fourth node.

In some implementations, the multiple wavelength channels comprises afirst set of wavelength channels and a second set of wavelengthchannels. The first set of wavelength channels and the second set ofwavelength channels are distinct, and the first set of wavelengthchannels received by the first AWG from the first node is directed tothe second node, and the second set of wavelength channels received bythe first AWG from the first node is directed to the fourth node.

FIG. 7 depicts a flow diagram illustrating an example process ofreconfiguring interconnectivity of a plurality of nodes coupled to aplurality of AWGs. Each node has a first and second output fiber, andeach first output fiber of each node is coupled to a different inputport of a first set of arrayed waveguide gratings (AWG), and each secondoutput fiber of each node is coupled to a different output port of asecond set of AWGs.

Further, each node includes a set of components for each AWG that thenode is coupled to. Additionally, each set of components includes aplurality of optical transmitters, where each optical transmitter istunable over multiple wavelength channels within a different wavelengthband; a band multiplexer to multiplex the multiple wavelength channelswithin each different wavelength band; a first output fiber to couple anoutput of the band multiplexer to one of the input ports of an AWG ofthe first set of AWGs; a band demultiplexer to demultiplex the multiplewavelength channels within each different wavelength band; a pluralityof receivers to receive wavelengths of light within the differentwavelength bands; and a first input fiber to couple one of the outputports of an AWG of the second set of AWGs the first AWG to an input ofthe band demultiplexer.

At block 705, a destination node for each wavelength channel emitted byeach tunable transmitter may be determined by a controller for each nodeof the plurality of nodes.

At block 710, each tunable transmitter may be caused by a controller toemit at a particular wavelength channel based on a goal.

In some implementations, the goal may be to save power by shutting downunneeded nodes and re-routing traffic from the unneeded nodes to othernodes. In this case, causing each tunable transmitter to emit at aparticular wavelength channel based on the goal may include causing eachtunable transmitter to emit at wavelength channels that are not routedby the plurality of AWGs to the unneeded nodes, and causing each tunabletransmitter at the unneeded nodes to stop emitting.

In some implementations, the goal may be to re-route traffic around afailed node through other operative nodes. In this case, causing eachtunable transmitter to emit at a particular wavelength channel based onthe goal may include causing each tunable transmitter to emit atwavelength channels that are not routed by the plurality of AWGs to thefailed node.

In some implementations, the goal may be to activate previously unusednodes to permit additional traffic to be routed to the previously unusednodes. In this case, causing each tunable transmitter to emit at aparticular wavelength channel based on the goal may include permittingeach tunable transmitter to emit at wavelength channels that are routedby the plurality of AWGs to the previously unused nodes.

Not all of the steps, or features presented above are used in eachimplementation of the presented techniques. Further, steps in processesmay performed in a different order than presented.

As used in the specification and claims herein, the singular forms “a,”“an,” and “the” include plural referents unless the context clearlydictates otherwise.

What is claimed is:
 1. A method of providing connectivity among aplurality of nodes comprising: causing a tunable wavelength opticaltransmitter at a first node to transmit over a first fiber an opticalsignal at a first wavelength channel, wherein the first fiber is coupledto an input port of a plurality of input ports of a first arrayedwaveguide grating (AWG), wherein the signal is routed to a first outputport of a plurality of output ports of the first AWG based on the firstwavelength channel and is transmitted over a second fiber to a secondnode; and causing a tunable wavelength optical transmitter at the secondnode to transmit over a third fiber the optical signal at a secondwavelength channel, wherein the third fiber is coupled an input port ofa plurality of input ports of a second AWG, wherein the signal is routedto a first output port of a plurality of output ports of the second AWGbased on the second wavelength channel and is transmitted over a fourthfiber to a third node.
 2. The method of claim 1, wherein the first nodeand the second node are part of a first set of nodes, wherein each nodeof the first set of nodes comprises: a plurality of opticaltransmitters, wherein each optical transmitter is tunable over multiplewavelength channels within a different wavelength band; a bandmultiplexer to multiplex the multiple wavelength channels within eachdifferent wavelength band; a band demultiplexer to demultiplex themultiple wavelength channels within each different wavelength band; aplurality of receivers to receive wavelengths of light within thedifferent wavelength bands from the band demultiplexer; an output fibercoupled to an output of the band multiplexer and coupled to one of theinput ports of the first AWG; and an input fiber coupled to an input tothe band demultiplexer and coupled to one of the output ports of thefirst AWG, wherein the second node and the third node are part of asecond set of nodes, wherein each node of the second set of nodescomprises: a plurality of optical transmitters, wherein each opticaltransmitter is tunable over multiple wavelength channels within adifferent wavelength band; a band multiplexer to multiplex the multiplewavelength channels within each different wavelength band; a banddemultiplexer to demultiplex the multiple wavelength channels withineach different wavelength band; a plurality of receivers to receivewavelengths of light within the different wavelength bands from the banddemultiplexer; an output fiber coupled to an output of the bandmultiplexer and coupled to one of the input ports of the second AWG; aninput fiber coupled to an input to the band demultiplexer and coupled toone of the output ports of the second AWG.
 3. The method of claim 2,further comprising rerouting the signal from the first node via a fourthnode to the third node and bypassing the second node, wherein reroutingthe signal comprises: causing the tunable wavelength optical transmitterat the first node to transmit the signal at a third wavelength channelover the first fiber to the input port of the first AWG, wherein thesignal is routed to a second output port of the first AWG based on thethird wavelength channel, and is transmitted over a fifth fiber to thefourth node; and causing a tunable wavelength optical transmitter at thefourth node to transmit the signal at a fourth wavelength channel over asixth fiber to a second input port of the second AWG, wherein the signalis routed to a second output port of the second AWG based on the fourthwavelength channel, and is transmitted over a sixth fiber to the thirdnode.
 4. The method of claim 3, wherein the multiple wavelength channelscomprises a first set of wavelength channels and a second set ofwavelength channels, wherein the first set of wavelength channels andthe second set of wavelength channels are distinct, and further whereinthe first set of wavelength channels received by the first AWG from thefirst node is directed to the second node, and the second set ofwavelength channels received by the first AWG from the first node isdirected to the fourth node.
 5. The method of claim 1, furthercomprising: determining an entity associated with the first, second, andthird nodes; permitting the signal to be transmitted at the firstwavelength channel from the first node to be routed to the second nodeby the first AWG only if the entity associated with the first node andthe entity associated with second node is the same; and permitting thesignal to be transmitted at the second wavelength channel from thesecond node to be routed to the third node by the second AWG only if theentity associated with the second node and the entity associated withthe third node is the same.
 6. A method of reconfiguringinterconnectivity of a plurality of nodes coupled to a plurality ofarrayed waveguide gratings (AWG), the method comprising: determining adestination node for each wavelength channel emitted by each tunabletransmitter for each node of the plurality of nodes; and causing eachtunable transmitter to emit at a particular wavelength channel based ona goal, wherein each node has a first and second output fiber, and eachfirst output fiber of each node is coupled to a different input port ofa first set of arrayed waveguide gratings (AWG), and each second outputfiber of each node is coupled to a different output port of a second setof AWGs, wherein each node comprises a set of components for each AWGthat the node is coupled to, wherein each set of components comprises: aplurality of optical transmitters, wherein each optical transmitter istunable over multiple wavelength channels within a different wavelengthband; a band multiplexer to multiplex the multiple wavelength channelswithin each different wavelength band; a first output fiber to couple anoutput of the band multiplexer to one of the input ports of an AWG ofthe first set of AWGs; a band demultiplexer to demultiplex the multiplewavelength channels within each different wavelength band; a pluralityof receivers to receive wavelengths of light within the differentwavelength bands; and a first input fiber to couple one of the outputports of an AWG of the second set of AWGs the first AWG to an input ofthe band demultiplexer.
 7. The method of claim 6, wherein the goal is tosave power by shutting down unneeded nodes and re-routing traffic fromthe unneeded nodes to other nodes, and further wherein causing eachtunable transmitter to emit a particular wavelength channel based on agoal comprises causing each tunable transmitter to emit wavelengthchannels that are not routed by the plurality of AWGs to the unneedednodes, and causing each tunable transmitter at the unneeded nodes tostop emitting.
 8. The method of claim 6, wherein the goal is to re-routetraffic around a failed node through other operative nodes, and furtherwherein causing each tunable transmitter to emit a particular wavelengthchannel based on a goal comprises causing each tunable transmitter toemit wavelength channels that are not routed by the plurality of AWGs tothe failed node.
 9. The method of claim 6, wherein the goal is toactivate previously unused nodes to permit additional traffic to berouted to the previously unused nodes, and further wherein causing eachtunable transmitter to emit a particular wavelength channel based on agoal comprises permitting each tunable transmitter to emit wavelengthchannels that are routed by the plurality of AWGs to the previouslyunused nodes.